<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            padding: 0;
            margin: 0;
        }
        body,html{
            height: 100%;
        }
        section{
            width: 100%;
            height: 100%;
            display: flex;
        }
        .one{
            width: 200px;
            height: 100%;
            background-color: yellow;
        }
        .two{
            flex: 1;
            height: 100%;
            background-color: pink;
        }
        @media screen and (max-width:1000px){
            .one{
                display: none;
            }
            .two{
                background-color: rgb(52, 202, 72);
            }
        }
    </style>
</head>
<body>
    <section>
        <div class="one"></div>
        <div class="two"></div>
    </section>
</body>
</html>